ASK AN EXPERT

Got a question about a health story in the news or a health topic? Here's your chance to get an answer. Send us your questions about general health topics, diet and fitness and mental health. If your question is chosen, it could be featured on CNN.com's health page with an answer from one of our health experts, or by a participant in the CNNhealth community.

Name*Location*Email*Question*

* CNN encourages you to contribute a question. By submitting a question, you agree to the following terms found below.

Select a topic? (optional)

You may not post any unlawful, threatening, libelous, defamatory, obscene, pornographic or other material that would violate the law. By submitting your question, you hereby give CNN the right, but not the obligation, to post, air, edit, exhibit, telecast, cablecast, webcast, re-use, publish, reproduce, use, license, print, distribute or otherwise use your questions(s) and accompanying personal identifying and other information you provide via all forms of media now known or hereafter devised, worldwide, in perpetuity. CNN Privacy Statment.

Thank you for your question!

It will be reviewed and considered for posting on CNNHealth.com. Questions and comments are moderated by CNN and will not appear until after they have been reviewed and approved. Unfortunately, because of the voume of questions we receive, not all can be posted.

Expert Q&A

Is a shorter but harder workout better?

Asked by Lori Wilson, Menomonee Falls, Wisconsin

No one has been able to answer this question for me. Is it better to exercise hard for a short period of time, or is it better to exercise moderately for a longer period of time? For example, let's say you can exercise hard for 10 minutes before your body makes you stop, but you can exercise moderately for 30 minutes or more. Which is better?

Expert Answer:

Hi Lori

The 2008 Physical Activity Guidelines for Americans released by the Department of Health and Human Services recommends that adults age 18 to 64 engage in at least 2.5 hours of moderate-intensity aerobic exercise (brisk walking, biking) or an hour and 15 minutes of vigorous activity (like running) each week. So with these guidelines in mind, the answer to your question depends on your exercise goals.

For heart health, it is probably better to exercise moderately for at least 30 minutes five times per week. For improving fitness levels, it may be better to exercise harder for a short period of time.

I think the best approach for health, fitness and weight loss includes exercising at a variety of intensities each week (doing one or two longer, moderate-intensity workouts and several shorter, more intense workouts) or incorporating interval training into your workouts. Interval training involves alternating periods of moderately intense exercise that last one to three minutes with short, more intense exercise periods lasting from 30 seconds to a minute.

By alternating high- and low-intensity exercise during the same workout, you are able to exercise at a higher overall average intensity, burn more calories and improve fitness. This type of training can also help prevent weight loss plateaus, which often occur during weight loss accompanied by exercise because the fitter or trimmer that you are, the fewer calories you burn doing the same workout.

I recommend that my patients incorporate interval training at least twice a week for 20 to 30 minutes. No special equipment is needed (although a heart rate monitor can be helpful for gauging how hard you are working) and interval training can be done either outdoors or indoors.

CNN Comment Policy: CNN encourages you to add a comment to this discussion. You may not post any unlawful, threatening, defamatory, obscene, pornographic or other material that would violate the law. All comments should be relevant to the topic and remain respectful of other authors and commenters. You are solely responsible for your own comments, the consequences of posting those comments, and the consequences of any reliance by you on the comments of others. By submitting your comment, you hereby give CNN the right, but not the obligation, to post, air, edit, exhibit, telecast, cablecast, webcast, re-use, publish, reproduce, use, license, print, distribute or otherwise use your comment(s) and accompanying personal identifying and other information you provide via all forms of media now known or hereafter devised, worldwide, in perpetuity. CNN Privacy Statement.

The information contained on this page does not and is not intended to convey medical advice. CNN is not responsible for any actions or inaction on your part based on the information that is presented here. Please consult a physician or medical professional for personal medical advice or treatment.